Integrin-mediated adhesion plays a central role in numerous cellular processes including proliferation, migration, and differentiation. Within the epidermis of the skin, integrin receptors are known to influence stem cell differentiation;however, the mechanism by which cues from the ECM coordinate with other signaling pathways to determine cell fate remains unclear. The overall goal of this research proposal is to investigate the interaction between integrin-mediated adhesion and beta-catenin related signaling pathways in the regulation of epidermal differentiation. The proposed studies will employ engineered polymer substrates to control the type, density, and spatial organization of cell-adhesive ligands presented to the cells. The influences of these defined cell-matrix interactions on epidermal differentiation will be examined using keratinocytes isolated from wild type mice and transgenic mice with inducible beta-catenin, Notch, and c-Myc expression. The central hypothesis for this work is that integrin-mediated adhesion to the extracellular matrix regulates keratinocyte differentiation and that these responses are modulated by the strength of beta-catenin signaling and other related pathways. This research will be carried out in three specific aims: Aim 1: Develop poly-(OEGMA) substrates presenting controlled densities and patterns of cell adhesive ligands to modulate keratinocyte adhesion and morphology. Aim 2: Examine the effects of integrin-mediated adhesion to engineered substrates on keratinocyte proliferation and in vitro differentiation. Aim 3: Investigate the interactions between integrin-mediated adhesion and beta-catenin related pathways in the regulation epidermal differentiation. The successful completion of this research proposal will provide significant insights into the interacting roles of multiple pathways involved in the regulation of epidermal differentiation. The long term objective is to establish novel experimental systems that will improve the fundamental understanding of stem cell lineage selection, differentiation, and self renewal. This research has important implications in the field of cancer cell biology. Since integrin and beta-catenin signaling also influence tumor development and invasion, insights into the behavior of epidermal stem cells will advance the current understanding of skin cancer pathology and aid in the development of therapeutic agents.